1. Field of the Invention
The present invention relates to fire-retarding articles made of a foraminous core and having a protective fire-retarding layer on the outside made of a hydrophilic polymer foam. Coating and molding methods are disclosed to provide the fire-retardant protective layer around the core.
2. Description of the Prior Art
Many different types of articles are made of foraminous materials. Flexible urethane foams, for example, have many useful advantages such as good cushioning properties, acoustical and thermal insulation, ease of processing, low cost and light weight. They are being widely used in cushioning materials in automobiles, rolling stocks, airplanes, chairs, sofas and mattresses. These conventional flexible polyurethane foams, however, present serious fire hazards. Attempts have been made to produce flame-retardant urethane foams by the use of flame-retarding raw materials or by after-treatment of the foam products. Although some of these materials can pass a cigarette burn test which has a mild ignition source, it is difficult to add a large amount of fire-retardant materials in the foam, and thus many of these foams are not effective under more severe ignition sources or burning conditions. In addition many of the fire-retardant chemicals required in these foams are expensive in nature, which in turn contributes to the high cost of the foam article.
Attempts have been made to provide a separate barrier layer for fire resistance when using polyurethane foams. One example, made by the Kimberly-Clark Corporation under the trademark KIMBAR, is a non-woven sheet made of wet-laid novoloid fibers, alone or in combination with a flame-retardant resin binder. Another barrier material, made by du Pont under the trademark VONAR, is an interliner of a carboxylated polychloroprene latex which is heavily loaded with chemical additives. This product is recommended to reduce the furniture burning rate for limited ignition situations such as in business and institutional furniture where there is a reduced likelihood of ignition to the upholstered furniture. If VONAR is ripped, cut or otherwise separated so as to expose the flammable cushioning material beneath it, the degree of protection provided by VONAR is reduced. Thus, this material is not recommended in areas where the cushions are susceptible to vandalism and intentional fire.
Another approach to provide a flame-retardant foam article is to fabricate the article out of a hydrophilic polyurethane foam containing substantial amounts of fire-retardant additives. U.S. Pat. No. 4,137,200 to Wood et al discloses a suitable foam and U.S. Pat. Nos. 3,897,372 to Kehr et al and 4,066,578 to Murch et al disclose foams with various fire-retardant additives. Although these foams have good fire-retardant properties, they do not necessarily possess optimum properties with regard to resiliency and flexibility desired for seat cushion use.
In addition to the use of flexible foams, other foraminous materials such as semi-rigid or rigid foams also perform useful functions such as providing for impact absorption, thermal insulation and the like. Such articles may also present serious fire hazards.
3. Objects of the Invention
It is an object of this invention to provide a protective layer on a foraminous core structure so as to reduce the burning tendencies of the resulting product.
It is another object of this invention to provide a flexible product made of a foam core material with a protective fire-retardant outer layer in which the resulting product has good flexibility and cushioning properties while providing good fire-retardant properties.
It is another object of the invention to employ a conventional bedding or cushioning material such as an innerspring construction or cotton linters and to provide an adherent fire-retardant protective outer layer in which the resulting product has good flexibility and cushioning properties while providing good fire-retardant properties.
It is a further object of this invention to provide a coating to a foam material which adheres well to the substrate and which is made of a hydrophilic polyurethane foam containing large amounts of fire-retardant additives.
It is a further object to provide a protective foam layer by a fabrication method in which the outside foam protective layer is initially formed on the inner surface of the mold, and then the core foam is added to fill the space inside the protective layer.
These and other objects of the invention will become apparent as the description of this invention proceeds.